In the summer of 1975, Teamsters President James Riddle Hoffa — Jimmy Hoffa — was already a legendary figure in both U.S. labor history and in American pop culture.

As a teenager in Detroit, he took to union organizing early on in the grocery business. He was smart and tough. With an emphasis on tough. A master strategist, he knew how to pick his targets, organize strikes and boycotts, and he rose through the Teamster ranks earning the deep loyalty of truckers and warehouse workers in a city that was becoming an industrial powerhouse.

By 1958, Hoffa was named president of the International Brotherhood of Teamsters.

The union was already deeply involved in corrupt activities.

Hoffa negotiated important national contracts for truckers, even as he battled federal officials looking into union corruption and ties to organized crime.

There were hearings on Capitol Hill in Washington, and famous clashes with a young lawyer working for the Senate Labor Committee named Robert Kennedy, televised in grainy black-and-white images to the masses.

Later, while serving as U.S. attorney general for his brother, President Kennedy, RFK continued to pursue Hoffa.

Eventually, in 1964, Jimmy Hoffa was sent to federal prison on charges of bribing a member of a grand jury. A fraud conviction followed, and after unsuccessful appeals, Hoffa would spend more than four years under lock and key.

President Nixon commuted his sentence in 1971 — with a catch. Hoffa would go free, but he could not participate in union activities. Once out of prison, Hoffa challenged that edict. He tried to regain power at the Teamsters. He now had powerful enemies there, who took over in his absence.

The union's corrupt activities also continued, which brings us to today's milestone anniversary.

On July 30, 1975, Hoffa had an afternoon meeting planned at the Macchus Red Fox restaurant in suburban Detroit, one of those dimly lit places with deep, plush booths. It's believed the others planning to attend were a pair of local organized crime leaders.

Hoffa pulled into the parking lot that day. He has not been seen since.

That's when the already sizable legend became one of the great, enduring mysteries of our times.

What happened to Jimmy Hoffa? Countless theories and conspiracies were born.

The mob grabbed him and disposed of the body. He now resides under a freeway in Detroit, or even more famously, under the end-zone of Giants Stadium in New Jersey.

Every year, it seems, new "evidence" is found. A new witness. Another theory. Yellow police tape goes up somewhere. Back-hoes and other equipment are brought in. A search ensues.

Then ... nothing. Hoffa was 62 years old when he disappeared.

But the legend lives on.

The Teamsters Unions marked the occasion Thursday with a statement calling James R. Hoffa "one of the greatest labor leaders in American history." It cites his crowning achievement — the 1964 National Master Freight Agreement — which brought more than 400,000 truckers under a single contract. The statement goes on, "Hoffa was devoted to his union and to his family" before crediting Hoffa, despite his criminal record, with the following: "He gave his life while fighting to remove corrupt elements from the union and return power to the members."

Today, the International Brotherhood of Teamsters is led by a familiar name, Jimmy's son James P. Hoffa, who was elected in 1999.

When the younger Hoffa was running for the union's top job, his name was an important calling card. His supporters liked to refer to him as "Hoffa Junior." But to his detractors, who saw the son as too much like his father, he was "Junior Hoffa."

James P. Hoffa made this promise back then: "The mob killed my father. If you vote for me, they will never come back."

Hoffa won the job his father once held, but he took over a union that was by then under strict federal oversight and monitoring as part of a plan to restore integrity and root out deep-seated, institutional organized crime ties. In January of this year, the feds decided that significant progress to that end had been achieved, announcing that the oversight would end in the next five years.

It's a complex story involving a large and important union, but it pales in comparison to that illustrious character named Jimmy Hoffa.